The invention generally relates to a probe head for a coordinate measuring machine. More specifically, the invention relates to a probe head comprising a stylus resiliently suspended in a housing, and a sensor arrangement for detecting deflections of the stylus relative to the housing.
A prior art probe head designed for determining dimensions of a shaft is disclosed by DE 37 21 682 A1. This probe head has an elongated arm with a spherical probe tip that bears against the circumference of a rotating shaft. The arm is part of a parallelogram-type structure whose articulations are formed by segments of diminished cross section that are designed in the manner of film hinges. The entire arrangement is designed in a single-piece fashion. In order to convert the movement of the arm with the probe tip into an electrically detectable signal, use is made of an inductive sensor arrangement in which a core moved indirectly by the probe tip dips into a measuring coil. As an alternative embodiment, a Hall element is proposed, but without specifying any details of the arrangement or the evaluation of the Hall voltage.
DE 198 23 059 C2 discloses a method and a device for detecting the spatial position of a body. Use is made of an array of 4×4 sensors, such as Hall sensors.
DE 37 08 105 A1 discloses a measuring probe for a coordinate measuring machine that proposes magnetoresistive sensors for three-dimensional position measurements. A stylus is situated with one of its poles opposite a resistor dependent on a magnetic field, the deflection of the stylus effecting a variation in the spacing between the magnetic pole and resistor.
DE 26 20 099 C2 discloses a probe head with a stylus that can be deflected in all directions. In order to measure and detect a movement of the stylus, use is made of an inductive sensor arrangement in which there are provided two inductive sensors on each of all three axes. The sensors are arranged on opposite sides of the stylus. The inductive sensors are connected up to form a bridge circuit.
DE 37 20 524 A1 discloses a caliper rule having a Hall sensor. The Hall sensor is located next to a magnet such that, in the absence of a ferromagnetic disturbance, the Hall element is penetrated symmetrically by the field lines of the magnet, the Hall voltage thereby being precisely zero. If a runner with the Hall sensor is displaced on the bar, ferromagnetic rungs of a ladder-type arrangement run past the Hall sensor and distort the magnetic field, with the consequence that the Hall element is permeated asymmetrically by field lines, a finite Hall voltage thereby being produced. The Hall voltage is fed to a threshold stage that forms pulses, which are subsequently counted in, order to determine the position of the runner on the bar.
DE 197 12 829 A1 discloses a device for detecting the position of a piston in a pneumatic cylinder. A Hall voltage with a polarity change is utilized, specifically by laterally passing a Hall by a magnet. The Hall signal is further processed by means of threshold stages.
DE 196 39 801 A1 discloses a sensor arrangement for detecting the position of movable parts by means of a Hall sensor in which the Hall sensor is laterally passed by a magnet in order to control a windscreen wiper system for a motor vehicle. Again, use is made of a threshold stage in order to process the Hall signal.